The present invention relates to a spot-type disc brake with at least one brake-shoe-actuating member disposed axially slidable in a brake caliper and adapted to be acted upon by a brake force, in particular a hydraulically actuated brake piston, and with a supporting surface taking the circumferential force which acts on the brake shoe during a braking operation.
It is known, for example, from German Patent DE-AS No. 1,251,102 to provide a pivotal connection between the brake piston and the brake pad of a fluid-pressure-actuated spot-type disc brake in order to absorb deformations of the brake members and counterbalance them so as to ensure both a perfect guiding of the brake piston and the brake pad and full engagement of the brake pad with the brake disc under all braking conditions. To this end, the ball-and-socket joint of the known spot-type disc brake, which connects the brake piston with the brake pad backing plate, is formed by a cup whose calotte-shell-shaped bottom is held in abutment with the mating calotte-shell-shaped piston end surface by means of a pin threadedly engaged with the piston and a plate-shaped disc, with a ring of an elastic material being inserted therebetween. However, the known spot-type disc brake does not permit a reduced brake fluid volume consumption during braking nor is its hydraulic efficiency increased.
In another known spot-type disc brake disclosed in U.S. Pat. No. 3,186,518, an inclined thrust member extends from a pivot point on the floating caliper substantially from the disc exit side to the brake shoe, supporting the latter diagonally. In this manner, when the brake shoe moves into engagement with the brake disc, a clamping torque is produced at the brake pad actuated by the inclined thrust member, which torque is transmitted through the floating caliper to the opposite brake shoe. In addition to the clamping force of the hydraulic piston/cylinder arrangement, a supplementary brake force is thereby generated creating a type of wedging action. In this case, a brake power assistance caused by the drag force of the brake disc is present.